Light structures sold as kits are popular due in part to their advantages in terms of cost, availability, aesthetics, and ease of assembly by consumers. Non-limiting examples of such structures include pavilions, sun shelters, gazebos, solariums, garden sheds and the like. These structures are usually made of metal such as light steel, aluminum, strong plastics such as acrylonitrile butadiene styrene (ABS) or polyvinyl chloride (PVC) or combinations of such materials.
An example of such a light structure is shown on FIG. 1, which is a perspective view of a sun shelter made by Sojag™ of Brossard, Quebec, Canada. A shelter 10 comprises a roof 12 supported by four (4) legs or pillars 14. The roof 12 is constructed of a four (4) peripheral beams 16 (two of which are shown), panels 18 of various shapes and sizes, and a top ridge 20. Several elongated rails 22 lead from the beams 16 to the top ridge 20 and maintain the panels 18 in place. Elongated and narrow plates (not shown) located underneath the roof 12 may be fastened to the rails 22, at a right angle therewith, to provide greater stability to the structure.
FIG. 2 is a front elevation view of a conventional single-piece rail. The rail 22 as introduced in the description of FIG. 1 is shown in front elevation. It has a generally constant cross-section, so the front elevation view of FIG. 2 equally represents the cross-section the rail 22 at other points along its length. Only a top surface 24 of the rail 18 is visible on FIG. 1; a bottom surface 26 would be visible from underneath the roof 12 of the shelter 10. Within the rail 22, generally hidden from view, internal braces 28 transmit and distribute loading charges that may be applied on the roof 10, for example as a result of snow accumulation, between the top and bottom surfaces 24 and 26 of the rail 22. On each side of the rail 22, an opening 30 is provided for insertion of side edges of the panels 18 when assembling the shelter 10. Hooks 32 are provided on each outer edge of the rail 22 for insertion of strips (not shown) used as water guards pressing against the edges of the panels 18.
As may be understood from a consideration of FIG. 1, two (2) or more panels may take place within a perimeter formed of the ridge 20, a pair of rails 22 and one of the beams 16. In an overlap area 34, a lower end of a first panel 18 located closer to the ridge 20 would extend slightly over an upper end of a second panel 18 located closer to the beam 16 so that rain falling on the roof 12 would not penetrate between these panels. Consequently, the openings 30 of the rail 22 need to accommodate twice the thickness of the panels 18 since this double thickness needs to be accommodated in the overlap area 34.
However, if the openings 30 are too narrow, assembly of the roof 12 will be difficult, require application of significant force to the panels 18, leading to possible damage. If the openings 30 are too wide, small unsightly gaps may remain visible between the panels 18 and the panels 18 may tend to move after the shelter 10 has been fully assembled.
Therefore, there is a need for improved techniques for assembling light structures.